The present invention relates to fixing devices and, in particular, to an electromagnetic induction heating type fixing device.
The present invention relates also to an image forming apparatus having an electromagnetic induction heating type fixing device.
In general, the electromagnetic induction heating type fixing device of this kind has a fixing member (roller or belt) whose outer peripheral surface is brought in pressure contact with a sheet (paper) conveyed, and an induction coil for heating the fixing member by electromagnetic induction. By heating a metal layer of the fixing member by electromagnetic induction caused by the induction coil, a toner image adhering to the sheet is melted by the heat of the fixing member and fixed onto the sheet.
Conventionally, a system for preventing an excessive temperature rise in the end portion of the fixing member (i.e., a region through which a small-size sheet does not pass) by movably providing a magnetic flux shield member in the vicinity of the end portion of the fixing member in the widthwise direction of the sheet and moving the position of the magnetic flux shield member according to the dimension (width dimension) in the widthwise direction of the sheet to be subjected to image fixing has been proposed (refer to, for example, JP H10-74009 A and JP 2006-195408 A).